Isotopes of technetium
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Technetium (43Tc) is the first of the two elements lighter than bismuth that have no non-radioactive isotopes; the other such element is promethium.[2] It is primarily artificial, only trace quantities existing in nature produced by spontaneous fission or neutron capture by molybdenum. The first isotopes to be synthesized were 97Tc and 99Tc in 1936, the first artificial element to be produced. The most stable radioisotopes are 98Tc (half-life of 4.2 million years), 97Tc (half-life: 2.6 million years) and 99Tc (half-life: 211,100 years).[3]
Thirty-three other radioisotopes have been characterized with atomic masses ranging from 85Tc to 120Tc.[4] Most of these have half-lives that are less than an hour; the exceptions are 93Tc (half-life: 2.75 hours), 94Tc (half-life: 4.883 hours), 95Tc (half-life: 20 hours), and 96Tc (half-life: 4.28 days).[3]
Technetium also has numerous meta states. 97mTc is the most stable, with a half-life of 90.1 days (0.097 MeV). This is followed by 95mTc (half-life: 61 days, 0.038 MeV), and 99mTc (half-life: 6.04 hours, 0.143 MeV). 99mTc only emits gamma rays, subsequently decaying to 99Tc.[3]
For isotopes lighter than the most stable isotope, 98Tc, the primary decay mode is electron capture, giving molybdenum. For the heavier isotopes, the primary mode is beta emission, giving ruthenium, with the exception that 100Tc can decay both by beta emission and electron capture.[3][5]
Technetium-99 is the most common and most readily available isotope, as it is a major fission product from fission of actinides like uranium and plutonium with a fission product yield of 6% or more, and in fact the most significant long-lived fission product. Lighter isotopes of technetium are almost never produced in fission because the initial fission products normally have a higher neutron/proton ratio than is stable for their mass range, and therefore undergo beta decay until reaching the ultimate product. Beta decay of fission products of mass 95-98 stops at the stable isotopes of molybdenum of those masses and does not reach technetium. For mass 100 and greater, the technetium isotopes of those masses are very short-lived and quickly beta decay to isotopes of ruthenium. Therefore, the technetium in spent nuclear fuel is practically all 99Tc.
One gram of 99Tc produces 6.2×108 disintegrations a second (that is, 0.62 GBq/g).[6]
Technetium has no stable or nearly stable isotopes, and thus a standard atomic weight cannot be given.
Stability of technetium isotopes
Technetium and promethium are unusual light elements in that they have no stable isotopes. The reason for this is somewhat complicated.
Using the liquid drop model for atomic nuclei, one can derive a semiempirical formula for the binding energy of a nucleus. This formula predicts a "valley of beta stability" along which nuclides do not undergo beta decay. Nuclides that lie "up the walls" of the valley tend to decay by beta decay towards the center (by emitting an electron, emitting a positron, or capturing an electron). For a fixed number of nucleons A, the binding energies lie on one or more parabolas, with the most stable nuclide at the bottom. One can have more than one parabola because isotopes with an even number of protons and an even number of neutrons are more stable than isotopes with an odd number of neutrons and an odd number of protons. A single beta decay then transforms one into the other. When there is only one parabola, there can be only one stable isotope lying on that parabola. When there are two parabolas, that is, when the number of nucleons is even, it can happen (rarely) that there is a stable nucleus with an odd number of neutrons and an odd number of protons (although this happens only in four instances: 2H, 6Li, 10B, and 14N). However, if this happens, there can be no stable isotope with an even number of neutrons and an even number of protons.
For technetium (Z=43), the valley of beta stability is centered at around 98 nucleons. However, for every number of nucleons from 95 to 102, there is already at least one stable nuclide of either molybdenum (Z=42) or ruthenium (Z=44). For the isotopes with odd numbers of nucleons, this immediately rules out a stable isotope of technetium, since there can be only one stable nuclide with a fixed odd number of nucleons. For the isotopes with an even number of nucleons, since technetium has an odd number of protons, any isotope must also have an odd number of neutrons. In such a case, the presence of a stable nuclide having the same number of nucleons and an even number of protons rules out the possibility of a stable nucleus.[7]
List of isotopes
nuclide symbol |
Z(p) | N(n) | isotopic mass (u) |
half-life | decay mode(s)[8][n 1] |
daughter isotope(s)[n 2] |
nuclear spin |
---|---|---|---|---|---|---|---|
excitation energy | |||||||
85Tc | 43 | 42 | 84.94883(43)# | <110 ns | β+ | 85Mo | 1/2−# |
p | 84Mo | ||||||
β+, p | 84Nb | ||||||
86Tc | 43 | 43 | 85.94288(32)# | 55(6) ms | β+ | 86Mo | (0+) |
86mTc | 1500(150) keV | 1.11(21) µs | (5+,5−) | ||||
87Tc | 43 | 44 | 86.93653(32)# | 2.18(16) s | β+ | 87Mo | 1/2−# |
87mTc | 20(60)# keV | 2# s | 9/2+# | ||||
88Tc | 43 | 45 | 87.93268(22)# | 5.8(2) s | β+ | 88Mo | (2,3) |
88mTc | 0(300)# keV | 6.4(8) s | β+ | 88Mo | (6,7,8) | ||
89Tc | 43 | 46 | 88.92717(22)# | 12.8(9) s | β+ | 89Mo | (9/2+) |
89mTc | 62.6(5) keV | 12.9(8) s | β+ | 89Mo | (1/2−) | ||
90Tc | 43 | 47 | 89.92356(26) | 8.7(2) s | β+ | 90Mo | 1+ |
90mTc | 310(390) keV | 49.2(4) s | β+ | 90Mo | (8+) | ||
91Tc | 43 | 48 | 90.91843(22) | 3.14(2) min | β+ | 91Mo | (9/2)+ |
91mTc | 139.3(3) keV | 3.3(1) min | β+ (99%) | 91Mo | (1/2)− | ||
IT (1%) | 91Tc | ||||||
92Tc | 43 | 49 | 91.915260(28) | 4.25(15) min | β+ | 92Mo | (8)+ |
92mTc | 270.15(11) keV | 1.03(7) µs | (4+) | ||||
93Tc | 43 | 50 | 92.910249(4) | 2.75(5) h | β+ | 93Mo | 9/2+ |
93m1Tc | 391.84(8) keV | 43.5(10) min | IT (76.6%) | 93Tc | 1/2− | ||
β+ (23.4%) | 93Mo | ||||||
93m2Tc | 2185.16(15) keV | 10.2(3) µs | (17/2)− | ||||
94Tc | 43 | 51 | 93.909657(5) | 293(1) min | β+ | 94Mo | 7+ |
94mTc | 75.5(19) keV | 52.0(10) min | β+ (99.9%) | 94Mo | (2)+ | ||
IT (.1%) | 94Tc | ||||||
95Tc | 43 | 52 | 94.907657(6) | 20.0(1) h | β+ | 95Mo | 9/2+ |
95mTc | 38.89(5) keV | 61(2) d | β+ (96.12%) | 95Mo | 1/2− | ||
IT (3.88%) | 95Tc | ||||||
96Tc | 43 | 53 | 95.907871(6) | 4.28(7) d | β+ | 96Mo | 7+ |
96mTc | 34.28(7) keV | 51.5(10) min | IT (98%) | 96Tc | 4+ | ||
β+ (2%) | 96Mo | ||||||
97Tc | 43 | 54 | 96.906365(5) | 4.2x106 a | EC | 97Mo | 9/2+ |
97mTc | 96.56(6) keV | 91.4(8) d | IT (99.66%) | 97Tc | 1/2− | ||
EC (.34%) | 97Mo | ||||||
98Tc | 43 | 55 | 97.907216(4) | 6.6x106 a | β− | 98Ru | (6)+ |
98mTc | 90.76(16) keV | 14.7(3) µs | (2)− | ||||
99Tc[n 3] | 43 | 56 | 98.9062547(21) | 2.111(12)×105 a | β− | 99Ru | 9/2+ |
99mTc[n 4] | 142.6832(11) keV | 6.0058(12) h | IT (99.99%) | 99Tc | 1/2− | ||
β− (.0037%) | 99Ru | ||||||
100Tc | 43 | 57 | 99.9076578(24) | 15.8(1) s | β− (99.99%) | 100Ru | 1+ |
EC (.0018%) | 100Mo | ||||||
100m1Tc | 200.67(4) keV | 8.32(14) µs | (4)+ | ||||
100m2Tc | 243.96(4) keV | 3.2(2) µs | (6)+ | ||||
101Tc | 43 | 58 | 100.907315(26) | 14.22(1) min | β− | 101Ru | 9/2+ |
101mTc | 207.53(4) keV | 636(8) µs | 1/2− | ||||
102Tc | 43 | 59 | 101.909215(10) | 5.28(15) s | β− | 102Ru | 1+ |
102mTc | 20(10) keV | 4.35(7) min | β− (98%) | 102Ru | (4,5) | ||
IT (2%) | 102Tc | ||||||
103Tc | 43 | 60 | 102.909181(11) | 54.2(8) s | β− | 103Ru | 5/2+ |
104Tc | 43 | 61 | 103.91145(5) | 18.3(3) min | β− | 104Ru | (3+)# |
104m1Tc | 69.7(2) keV | 3.5(3) µs | 2(+) | ||||
104m2Tc | 106.1(3) keV | 0.40(2) µs | (+) | ||||
105Tc | 43 | 62 | 104.91166(6) | 7.6(1) min | β− | 105Ru | (3/2−) |
106Tc | 43 | 63 | 105.914358(14) | 35.6(6) s | β− | 106Ru | (1,2) |
107Tc | 43 | 64 | 106.91508(16) | 21.2(2) s | β− | 107Ru | (3/2−) |
107mTc | 65.7(10) keV | 184(3) ns | (5/2−) | ||||
108Tc | 43 | 65 | 107.91846(14) | 5.17(7) s | β− | 108Ru | (2)+ |
109Tc | 43 | 66 | 108.91998(10) | 860(40) ms | β− (99.92%) | 109Ru | 3/2−# |
β−, n (.08%) | 108Ru | ||||||
110Tc | 43 | 67 | 109.92382(8) | 0.92(3) s | β− (99.96%) | 110Ru | (2+) |
β−, n (.04%) | 109Ru | ||||||
111Tc | 43 | 68 | 110.92569(12) | 290(20) ms | β− (99.15%) | 111Ru | 3/2−# |
β−, n (.85%) | 110Ru | ||||||
112Tc | 43 | 69 | 111.92915(13) | 290(20) ms | β− (97.4%) | 112Ru | 2+# |
β−, n (2.6%) | 111Ru | ||||||
113Tc | 43 | 70 | 112.93159(32)# | 170(20) ms | β− | 113Ru | 3/2−# |
114Tc | 43 | 71 | 113.93588(64)# | 150(30) ms | β− | 114Ru | 2+# |
115Tc | 43 | 72 | 114.93869(75)# | 100# ms [>300 ns] | β− | 115Ru | 3/2−# |
116Tc | 43 | 73 | 115.94337(75)# | 90# ms [>300 ns] | 2+# | ||
117Tc | 43 | 74 | 116.94648(75)# | 40# ms [>300 ns] | 3/2−# | ||
118Tc | 43 | 75 | 117.95148(97)# | 30# ms [>300 ns] | 2+# |
- ^ Abbreviations:
EC: Electron capture
IT: Isomeric transition - ^ Bold for stable isotopes, bold italics for nearly-stable isotopes (half-life longer than the age of the universe)
- ^ Long-lived fission product
- ^ Used in medicine
Notes
- Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
- Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC, which use expanded uncertainties.
References
- ^ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
- ^ "Atomic weights of the elements 2011 (IUPAC Technical Report)" (PDF). IUPAC. p. 1059(13). Retrieved August 11, 2014. – Elements marked with a * have no stable isotope: 43, 61, and 83 and up.
- ^ a b c d "Technetium". EnvironmentalChemistry.com.
- ^ "Ground and isomeric state information for 120Tc". National Nuclear Data Center, Brookhaven National Laboratory.
- ^ N. E. Holden (2004). "Table of the Isotopes". In D. R. Lide (ed.). CRC Handbook of Chemistry and Physics (85th ed.). CRC Press. Section 11. ISBN 978-0-8493-0485-9.
{{cite book}}
: Unknown parameter|nopp=
ignored (|no-pp=
suggested) (help) - ^ The Encyclopedia of the Chemical Elements, p. 693, "Toxicology", paragraph 2
- ^ Radiochemistry and Nuclear Chemistry. The isotope technetium-97 decays only by electron decay and could be inhibited from radioactive decay by fully ionizing it.
- ^ "Universal Nuclide Chart". nucleonica.
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suggested) (help)
- Isotope masses from:
- G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A. 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001. Archived from the original (PDF) on 2008-09-23.
{{cite journal}}
: Unknown parameter|deadurl=
ignored (|url-status=
suggested) (help)
- G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A. 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001. Archived from the original (PDF) on 2008-09-23.
- Isotopic compositions and standard atomic masses from:
- J. R. de Laeter; J. K. Böhlke; P. De Bièvre; H. Hidaka; H. S. Peiser; K. J. R. Rosman; P. D. P. Taylor (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry. 75 (6): 683–800. doi:10.1351/pac200375060683.
- M. E. Wieser (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry. 78 (11): 2051–2066. doi:10.1351/pac200678112051.
{{cite journal}}
: Unknown parameter|laysummary=
ignored (help)
- Half-life, spin, and isomer data selected from the following sources. See editing notes on this article's talk page.
- G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A. 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001. Archived from the original (PDF) on 2008-09-23.
{{cite journal}}
: Unknown parameter|deadurl=
ignored (|url-status=
suggested) (help) - National Nuclear Data Center. "NuDat 2.1 database". Brookhaven National Laboratory. Retrieved September 2005.
{{cite web}}
: Check date values in:|accessdate=
(help) - N. E. Holden (2004). "Table of the Isotopes". In D. R. Lide (ed.). CRC Handbook of Chemistry and Physics (85th ed.). CRC Press. Section 11. ISBN 978-0-8493-0485-9.
{{cite book}}
: Unknown parameter|nopp=
ignored (|no-pp=
suggested) (help)
- G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A. 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001. Archived from the original (PDF) on 2008-09-23.